Field of the Invention
The present invention relates to an intermediate electronic device, and in particular to an intermediate electronic device that uses a power transmission unit.
Description of the Related Art
Typically, there are two types of electric power transmission regulations for Universal Serial Bus (USB): USB 2.0 and USB 3.0. Under the electric power transmission regulation of USB 2.0, the maximum current value is 500 mA and the maximum voltage value is 5 V, which are transmitted by USB power (VBus). The electric power transmission regulation of USB 2.0 allows a maximum power transmission of 2.5 Watt. Likewise, under the electric power transmission regulation of USB 3.0, the maximum current value is 900 mA and the maximum voltage value is 5 V, which are transmitted by USB power (VBus). The electric power transmission regulation of USB 3.0 allows a maximum power transmission of 4.5 Watt.
Recently, Universal Serial Bus (USB) is widely used, so a new USB Power Delivery specification is proposed. The new USB Power Delivery specification has a plurality of crucial features. Firstly, the maximum current value is increased to 5 A and the maximum voltage value is increased to 20 V, which are transmitted by USB power (VBus). That is to say, the new USB Power Delivery method allows a maximum power transmission of 100 Watt, so the charging time is drastically decreased. Secondly, under the conventional electric power transmission regulations, power supply is one-way (unidirectional). For example, the electric power is transmitted from the host system to the electronic device. However, the new USB Power Delivery specification defines a switchable electric power transmitting direction. For example, while the electronic device is able to receive electric power from the external power source, the electronic device is able to supply electric power of the external power source to the host system. Thirdly, electronic devices that have adopted the new USB Power Delivery specification are compatible with electronic devices that have adopted the conventional electric power transmission regulations (for example, electronic devices that have adopted USB 2.0 and USB 3.0).
The conventional chip controller of an electronic device has one pin, arranged to connect to a USB power line to detect whether the electronic device is connected to host system or not. When the USB power line is connected to the host system, the voltage of USB power acts as a detection signal (VBus_DET) and then is transmitted to the chip controller via the pin. When the chip controller detects that the electronic device is connected to the host system, the chip controller sequentially starts to work. In other word, the voltage of USB power can be regarded as an enable signal to enable the chip controller of the electronic device. The enable signal represents the detection signal of USB power herein and hereafter.
Under the conventional electric power transmission regulations, the voltage of USB power is only 5V, so the USB power can act as the enable signal directly and is directly transmitted to the chip controller of the electronic device without making the chip controller break down or burn out. However, under the new USB Power Delivery specification, the maximum voltage is 20 V, which is transmitted by USB power (VBus). The chip controller of the electronic device may be damaged or burn out when USB power with 20 V directly acts as the enable signal and is directly transmitted to the chip controller.
Therefore, there is a need to present a new electronic device, such that the new electronic device can work normally under the high voltage provided by USB power (VBus) without making the chip controller of the electronic device break down or burn out.